1. Field of the Invention
The invention relates to an electrical modular terminal, especially for connection of a current transformer, with a terminal housing, with at least two conductor connector elements which are located in the latter, and with at least two current bars, the current bars each having a connector section and a first contact section, the connector sections being assigned to a respective conductor connector element and the first contact sections together forming an elastic contact zone for accommodating the plug of a test plug or power plug, the first contact sections being spaced apart from one another and only with the plug inserted being connected to one another in an electrically conductive manner via the plug. In addition, the invention relates to a modular terminal block formed of at least two electrical modular terminals which are located next to one another and of at least one plug-in jumper which has at least two legs.
2. Description of Related Art
Electrical modular terminals have been known for decades and are used in the millions in wiring of electrical systems and devices. The terminals are often locked onto mounting rails which for their part can be located in a plurality in a switchgear cabinet. In addition, the modular terminals can, however, also be attached alone or in general severally as a modular terminal block in a wall opening, especially in an opening in a switchgear cabinet wall. This has the advantage that one side of the terminals, the operator side, is accessible from outside the switchgear cabinet without the switchgear cabinet having to be opened and only the other side of the terminal, the connecting side, is accessible only when the switchgear cabinet has been opened.
Conductor connector elements in modular terminals are predominantly screw terminals or tension spring terminals. The terminal principle for tension spring terminals is similar to that of the screw technology. While in a screw terminal a tension sleeve draws the conductor against the current bar by the actuation of the terminal screw, in the tension spring terminal this task is assumed by the tension spring. In addition however insulation piercing connecting terminals or leg spring terminals can also be used.
Electrical terminals are generally connecting terminals so that they have at least two conductor connector elements which are electrically connected to one another via an electrically conductive connecting bar, the current bar. In addition to this basic type of modular terminal which is often also called a feed-through terminal, there are a plurality of different modular terminal types which are specially matched to the respective applications (compare, Phoenix Contact Catalog Modular Terminals CLIPLINE 2011, pages 2-11). Examples are protective conductor terminals, isolating blade terminals and installation terminals.
In switching, measuring and control technology feed-through terminals with a disconnect possibility are the standard. The disconnection possibility which is implemented in the electrical modular terminal, i.e., the disconnect provided in the current bar makes it possible to insert different plugs with different function into the terminal housing of the modular terminal which then make contact with the current bar at the disconnect. In addition to simple disconnect plugs or through connectors, plugs can also be especially test plugs which can have special components and which enable testing of proper operation of the circuit which is connected to the modular terminal. Since the electrical modular terminals are generally made disk-shaped, they are generally mated to several other electrical modular terminals into a modular terminal block. A number of test plugs which corresponds to the number of modular terminals can then be plugged into such a modular terminal block.
German Patent 10 2005 025 108 B3 discloses a device for testing of a protective, measuring or counting apparatus, for example, a protective line relay of a high voltage or medium voltage system, which has a pole strip which can be connected to the electrical apparatus with several successively arranged pole openings and one plug block with a number of pole tongues which corresponds to the number of pole openings. An individual pole strip module of the pole strip consists of a housing in which there are two insert contacts for connecting the lines and spring-loaded contact clips which are connected to the insert contacts. The two contact clips can make contact with the pole tongue of a plug, the pole tongue of the plug having two pole segments which are separated from one another by an insulating segment. The insulating segment together with the corresponding pole opening in the pole strip module forms a polarization which ensures that only one plug with a certain pole tongue can be inserted into a certain pole opening of a pole strip.
In the state of the plug or the pole tongue not inserted into the pole strip, the two contact clips make contact with one another so that the two insert contacts are electrically connected to one another in an electrically conductive manner and a current can flow via a connected pole strip. If the plug with its pole tongue has been pushed completely into the pole opening, the two contact clips are electrically isolated from one another and the current flow is routed via the plug so that a test process can be carried out.
German Patent Application DE 10 2006 052 894 A1 and corresponding U.S. Pat. No. 7,666,037 B2 discloses a modular terminal, a test plug and a test terminal block consisting of a plurality of modular terminals located next to one another and a corresponding number of test plugs, the individual modular terminals and the individual test plugs being similar in basic principle to the pole strip modules and pole plugs known from DE 10 2005 025 108 B3.
In order to ensure reliable and defined contact states when the test plug is plugged into the test opening, in this known electrical modular terminal, the current bars are made such that they form two contact zones which are located in succession in the insertion direction of the contact plug of a test plug. Forming a defined second contact zone which is located in the insertion direction of the contact plug upstream of the first contact zone ensures that when the contact plug is inserted first a reliable electrical connection between the contact plug and the two current bars takes place before the first contact zone is opened as the contact plug continues to be inserted, as a result of which the two current bars are then electrically isolated from one another.
It is common to the above described known modular terminals or test terminal blocks that the two current bars make contact with one another so that the conductor connector elements are connected to one another in an electrically conductive manner if a plug is not plugged into the modular terminal. Conversely, if a plug is (completely) plugged into the modular terminal, the contact zone is interrupted so that the conductor connector elements are also electrically isolated from one another.
In addition to these modular terminals or test terminal blocks, test isolation blocks are also known, especially those from the Russian company Cheaz in which the elastic contact sections of the current bars which together form an elastic contact zone are spaced apart from one another and are only connected to one another in an electrically conductive manner when a plug of a power plug or test plug is plugged into the contact zone. The electrically conductive connection between the contact sections or between the current bars takes place via the inserted plug which for this purpose has two interconnected contact sections which make contact with the contact sections of the current bars when the plug has been plugged in.
In these test isolation blocks which are common especially in Eastern Europe and Russia, the conductor connector elements which are assigned to one another are only connected to one another in an electrically conductive manner when a corresponding power plug is plugged into the modular terminal or into the terminal block. These modular terminals or terminal blocks are used especially for connection of current transformers. One important functional feature consists in that the power transformers are shorted as soon as the test plug or the power plug is pulled out of the modular terminal or the terminal block.
For this purpose, in the known test isolation blocks, there are jumper plugs via which at least two adjacent current bars are connected to one another in an electrically conductive manner so that the assigned conductor connector elements are short-circuited. In this way, then the current transformers which are connected to the conductor connector elements are also short-circuited. The jumper plugs are located between the contact sections of the current bars, which sections are opposite one another, such that they make contact with one contact section of a current bar when a plug has not been plugged in. If a test plug or power plug is plugged into the electrical modular terminal or into a test terminal block, the contact sections of two current bars, which sections are opposite one another, are forced somewhat apart. This leads first of all to the contact sections being connected to one another via the electrically conductive plug. Moreover, the insertion of the plug into the contact zone however also leads to the connection between the contact section and one leg of the jumper plug being interrupted since the elastic contact section is forced away from the rigidly arranged jumper plugs by inserting the plug.
In the test terminal blocks which are known from the prior art, an electrically conductive connection between adjacent contact sections or current bars is thus ensured by the jumper plugs. This transverse bridging is automatically interrupted when a test plug or power plug is plugged in, at the same time the contact sections which are assigned to one another being electrically connected to one another in an electrically conductive manner via the plug.
Although these test isolation blocks have proven themselves in practice for decades, they also have some disadvantages. The disadvantages consist especially in that the structure and the mounting of the test isolation blocks are relatively involved. In particular, the mounting of the jumper plugs on the bottom of the housing of the test terminal block is relatively laborious, since the elastic contact zones must be deflected against their spring force for this purpose. At the same time, the jumper plugs must be fastened with a screw to the bottom of the housing, to ensure that the contact sections which have made contact with the jumper plug are deflected equally so far that equally good contact between the jumper plug and the contact sections is also ensured later. Finally there is the risk that the elastic current bars which are held only by a threaded rod will twist in the mounting of the jumper plugs; this can likewise have an adverse effect on the electrical contact between the contact section and the jumper plug.